In a conventional computer network (e.g., the Internet), computers communicate over a network infrastructure made up of interconnected nodes, such as routers and/or switches, connected by communication links such as optical fiber, copper cable, and wireless links. Typically, the topology of the network infrastructure is configured in such a way that the infrastructure contains more than one path through which data may be carried from one computer to another. The topology, for example, may include a partial mesh configuration, where a node is connected to multiple other nodes. A router in such a network, therefore, may contain a plurality of interface ports for connection to multiple neighboring routers.
Such a router typically receives data in discrete units (herein referred to as “packets,” which may include frames, cells, packets, or any other fixed- or variable-sized unit of data) at one or more of its ingress interface ports. The router examines destination address information embedded in the packets and determines the appropriate egress interface ports for outputting the respective packets, typically by performing a table lookup. To construct and update tables, routers may use dynamic routing protocols to systematically exchange information with other devices in the network to obtain a view of the network topology (this information being maintained in a routing database, such as one or more routing tables). Based on this information, the router constructs and updates a forwarding table, which associates ranges of destination addresses to respective egress interface ports.
In some cases, however, such use of forwarding tables may be inadequate. By relying on destination addresses to determine the appropriate egress interface port for packets, traditional routers do not distinguish packets according to other criteria. It may be desirable to use other criteria to, for example, facilitate traffic engineering of certain types of packets (i.e., select egress interface ports based on packet type as well as destination address).
In addition, in certain circumstances, the traditional use of forwarding tables may be inadequate to implement virtual private networks (VPNs). In cases where a single router forwards traffic for two separate VPNs, the router needs to ensure that traffic from one VPN is not sent to the other VPN. One proposed solution is to bind one or more ingress interface ports and one or more egress interface ports to each VPN. In this way, the bound ingress and egress interface ports only carry traffic for one VPN, allowing the router to readily maintain separation of traffic for each VPN.
In some cases, however, the network configuration may be such that traffic from two VPNs is intermingled and received at a single ingress interface port of a router. This may happen, for example, where the traffic from the two VPNs is carried over an open access network in which traffic separation is not maintained before arriving at the router. One potential solution is to inject tags into each packet to uniquely identify the VPN from which the packets came. This may be undesirable because additional components or enhancements would be required at each source computer in the VPN to generate tags and at the router to identify the tags and separate the different VPN traffic. Another solution is to use policy-based routing, which involves statically configuring the forwarding table to forward packets according to criteria other than destination address. This may also be undesirable because static policies are typically configured manually and are not updated dynamically as the state of the network changes. Policy-based routing may also require the use of additional components or enhancements.
Thus, there is a need for an invention that more adequately addresses problems occurring in the network.